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V. s DEPAR \WY.\ X I »l \< iRICI I I I l< I 
0MOLOG1 No. 158. 

I O. H< W ARD, Kninmologitt and Chirf ol Bufe.ii. 


1". M. WEBSTER, 
In < Tuargt of Ctr 

r IRS— 12 



L. O. Howard, Entomologist and chief of Bureau. 

C. L. Marlatt, Entomologist and Acting Chief in Absence of Chief. 

R. S. Clifton, Executive Assistant. 

W. F. Tastet, Chief Clerk. 

F. H. Chittenden, in charge of truck crop and stared product insi ct investigations. 

A. D. Hopkins, in charge of forest insect investigations. 

W. I>. Hunteb, in charge of southern field crop insect investigations. 

F. M. Websteb, in charge of cereal and foragt insect investigations. 

A. L. Qtjaintance, i/n charge of deciduous fruit insect investigations. 

E. F. Phillips, in charge of bee culture. 

D. M. Rogers, i/n charge of preventing spread of moths, field work. 

Roll.v P. Currie, in charge of editorial work. 

Mabel Colcord, in charge of library. 

Cereal and Fobage Insect Investigations. 

F. M. Webster, /"// charge. 

Geo. I. Reeves, VT. J. Phillips. C. N. Ainslie. E. O. (J. Kelly. T. D Crbahns, 
Harry S. Smith, Geo. <;. Ainslie. .1. A. Hyslop, W. II. Walton. J. T. Monell, 
J. J. Davis, T. H. Parks, R. A. Vickery. V. L. Wii.permvtii. E. <;. Smyth, 
Herbert T. Osborn, Philip Luginbill, C. W. C-BfcEL, E. J. Vosler. R. N. Wil- 
son, Vebnon King, George R. Smith, Irving Crawford, entomological as- 

Nettie S. Klopeer. Ellen Dashiell, preparators. 

Miriam Welles Reeves, collaborator. 

Circular No. 158. 


United States Department of Agriculture, 

L. O. HOWARD, Entomologist .ml Chid «.f Hurenu. 


yobia prat i n*h < iarman. > 
By r. M w i B8i 
In Cha real 'iinl Foraffi Insect Investigations. 


The minute organism known ;i- the clover mite (fig. Ii is : • 
true insect, but belongs, with the spiders, to a rery extensive group 
the adults of which possess 
eight legs, whereas true in- 
sects have only six legs. 

There are a greal many 
species of these mite- and 
they differ widely among 
themselves in habits. Sonic 
make galls on the leaves of 
trees and shrubs : some, like 
the one which commonly at- 
tacks the currant, arc known 
as blister mites, as they 
cause blisters on leave-: 
others are para-it ic on man. 
as the itch mite; while -till 
others, like the Trombidium, 
arc parasitic on insects. 
Another. P< dit uloid< s >•• n- 
Nev p., is parasitic 
on insects hut also attack- 
man. The one here treated 
lives on the surface of 
leave.- of trees and plant-. 
but does not cause galls or 
blisters. It is a near relative 
of the notorious red spider. 

The clover mite, also known a- the brown mile, i- of a twofold 
interest It attack.- the leave.- of clover, grasses, and fruit and other 


i. — The clover ml 

Enlarcod : minimi size shown by line at ri^-ht. 


trees, feeding upon and often destroying (hem; beside-, during- winter 
and spring it frequently swarms in dwellings, often crawling about 
in myriads over windows, furniture, picture-, curtains, etc. 

The species was first described in 1885. 1 but it was observed in great 
abundance about Washington, D. C. by Mr. Theodore Pergande, of 
the Bureau of Entomology, as early as 1878. While described as a 
clover-infesting species, having been found infesting clover leaves by 
both Mr. Pergande and Prof. IT. Garman, yet taken as a whole 
throughout its known area of distribution it is probably of more im- 
portance to the fruit grower than it is to the farmer. While east of 
the semiarid region it is found largely on clover and bluegrass, it 
is at present largely an orchard pest west of about longitude 100°. 

Fig. 2. — Map showing the distribution of the clover mite {Bryobia pratensis) in the 
United States in 1911. (Original! 


With the possible exception of Georgia the pest seems to occur 
generally over the whole country, except perhaps in the Gulf States 
and the Dakotas, though just why it should not be found even there 
can not now be explained. (See map, fig. 2.) Mr. Marlatt 2 states 
that it has been reported from Tennessee, and in the Sierra Nevada 
Mountains in California and Rocky Mountains in Montana at ele- 
vations of from 7.000 to 8.000 feet, but exact localities are not given. 

The mite was described from the leaves of red clover (Trifolium 
pratense) from which it derives its last or specific name. Accom- 

1 Fourteenth Rept St. Ent. 111., pp. 73-74, 1885. 
2 Cir. 19, Div. Ent., U. S. Dept. Agr., 1897. 


panying the original description is the following note b\ Dr. S. \. 
Forbes, State entomologisl of Qlinois: 

ai Normal, ea May, the general occurrence 'i conapli 

brownish red ■■ ■ i i •- was noticed upon clover and bluegrass the former "i" these 
plants, especially, sometlmef Buffering Beverelj from the peal The lea i 
the clover turned yellow and their growth w ed where the mite wai 

■bandant I'be effecl upon the blues. similar. 

\- a matter of fact, the bureau records contain reports of the 
occurrence "I" the species over the territory indicated by the map 
(fig. •_'). These records illustrate its great varietj of food plant- a- 
well as th«' effect of climatic and other natural conditions upon its 
habits; they are, however, far too voluminous to include in a publi- 
cation of the nature of this circular. 


These mites are sufficiently shown in figure 1 to obviate the n< 
-itv for a lengthy description. When young thej are of a decidedly 
red color, but become brown when fulh developed, even then being 
smaller than the head of a pin. They are very familiar objects 
moving about over clover leaves that have a more or less whitish 
appearance. The discoloration of the leaves is in part due to the 

feeding of the mitt'-, and also to tin' tiny white web that they leave 
behind them a- the\ move about. The eggs are minute, round, red, 
and shining. 


From the foregoing it will be observed that this mite i- ;i | 
feeder and may be expected to attack clover-, alfalfa, bluegrass, and 
probably other grasses, among them timothy. It may affect oats and 

probably other grains including buckwheat. Mr. <i *ge P. Weldon 

■ all- attention to the fact that it had not been observed attacking 
apricot or quince and appeared less on peach than on most other 
fruit- in Colorado. 1 

Judging from what we know of an allied species, Tetranychtu 
h'nhiu tdatus Harvey, the jh*- t i- likely to become more abundant 
and injurious in the drier sections of the country than where the 
atmosphere i- more humid. It does not necessarily follow that the 
mite will attack the fob a ire of the tree on which it has deposited eggs. 

-i \-c\ \t. HIST 'i;i . 

Throughout the eastern portion of the country the life cycle and 
seasonal history of this species probably do not materially differ 
from those of other mite.-. With the coming >•( cold weather in late 

' i •■ dt 

«Bul. 162 jr. Coll. Exp. Sta.. p. 6. 1909. 


autumn or early winter the mites apparently cease to deposit egg-. 
and thus operations are simply suspended until the coming of warm 
weather in spring, when the eggs promptly hatch young mites. This 
is clearly shown by the observations of Mr. Pergande. 

A- will be observed, the presence of mies in dwellings during 
fall and spring is of common occurrence. Do they deposit eggs and 
do these eggs hatch there { It may be stated thai both eggs and mite 
were received from "Williainsport. Pa.. December 11. 180G, and that 
the eggs hatched en route. Also, as observed by the writer, the mite- 
entering a dwelling in Lafayette. Ind.. during December. 1880, when 
the weather was very mild, were at first full grown, but young 
appeared later in the month. Whether nates seek out dwellings in 
which to continue reproduction but die out for lack of food, or 
whether they enter them for the purpose of hibernation, is not clear. 
It is very clear, however, that they do not go into hibernation in 
May. a time when their occurrence in dwelling- is of equally common 
occurrence. Furthermore, our notes show that complaints of these 
mites entering dwellings almost invariably come from the eastern and 
cooler sections of the country, the reports from McCook, Xebr., and 
Denver, Colo., being the only exceptions in the West. Mr. George P. 
Weldon. who studied the species in Colorado. 1 states that it winters 
there principally in the egg stage and that practically no living 
mites can be found abroad after August 1. Hatching begins about 
May 1. and there are probably three generations annually in that 


Tobacco preparations applied in the form of a liquid spray are 
quite effective in destroying the mite, but do not destroy the egg, 
and therefore offer only temporary relief. Mr. Weldon found 
that flowers of sulphur dusted on foliage during early morning 
was more effective in destroying the mites. A liquid spray of 1 
pound flowers of sulphur mixed in -1 gallons of weak soapsuds, 1 
pound of soap to 100 gallons of water, was very effective and ap- 
peared to be lasting in its effects. This last can be easily applied 
to lawn-- and grounds where the mites are at work and also in 
field- of clover or alfalfa in case the depredations are confined to 
-mall spots or areas. The eggs can be destroyed on the trunks of 
trees by the use of strong kerosene emulsion. The writer has re- 
ceived reports of good results in driving the mites away from dwell- 
ings by placing oil of pennyroyal in small shallow dishes in the 
looms where the mites occur. This measure does away with the 
disagreeable feature of fumigation with fumes of sulphur or dust- 
ing with insect powder, and the odor of the oil is not disagreeable 
to people using the rooms. 

1 Loc. cit., p. 3, October. 1909. 

Till ii i>\ I i; Ml I 1 . O 

s \ i i 1: m i \ l \i II S. 

The insect enemies "l" ilii- mite, o far as recorded, are eerj few. 

( tetober 28, L889, Mi. Perg md< reared one of the common clothes 
moths (Tineola hiseUiella Hiibn.) from small caterpillars that be 
had observed to feed upon tl 

Mr. Weldon ' gives as enemies "f the red pider (Tetranychtu 
h'nini< uliit'ts Harv.) a minute black lady-beetle, Scymnu* punctum 
Lee. MiL r - 3) and lace-winged flies. \- there are many speci< 

* O 

IT.. '■ S "riiMu.« punctum, a laih beetle enemy of the clover mlt' Bgg; ''• larva; 

e, papa; •'. adult. All n . '. ■ . Red iwn fr..m Weldon: <'. original. 

the Scymnus and of lace-winged flies, ii is nol at all unlikely that 
some of them prey upon the clover mite. 

A.pproi ill : 
James Wn 

i y of . \>i> icvltun . 

Washington, D. ( .. April 18, 1912. 

. I 

ent or D 

Offic - copy 


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